66672781 has 12 divisors (see below), whose sum is σ = 79024572. Its totient is φ = 56067648.

The previous prime is 66672737. The next prime is 66672787. The reversal of 66672781 is 18727666.

It can be written as a sum of positive squares in 2 ways, for example, as 52490025 + 14182756 = 7245^2 + 3766^2 .

It is not a de Polignac number, because 66672781 - 2⁹ = 66672269 is a prime.

It is a super-2 number, since 2×66672781² = 8890519452547922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66672787) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10240 + ... + 15433.

It is an arithmetic number, because the mean of its divisors is an integer number (6585381).

Almost surely, 2^66672781 is an apocalyptic number.

It is an amenable number.

66672781 is a deficient number, since it is larger than the sum of its proper divisors (12351791).

66672781 is a wasteful number, since it uses less digits than its factorization.

66672781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25740 (or 25733 counting only the distinct ones).

The product of its digits is 169344, while the sum is 43.

The square root of 66672781 is about 8165.3402256122. The cubic root of 66672781 is about 405.4925288627.

The spelling of 66672781 in words is "sixty-six million, six hundred seventy-two thousand, seven hundred eighty-one".